smooth boundaries of a masked area

Dear all,

I would like to mask a region in a tripolar grid. Outside this region the values should be 0. In the transition zone (e.g. 3°) I want the values to decay (linearly or exponentially) to 0.
My current approach is to create a weight file with values from 0 to 1 on a regular grid. I will then interpolate it to the tripolar grid and multiply it with the data.

Ho can I create this transition zone in NCL? For straight boundaries in N/S or E/W direction I could introduce some latitude/longitude dependence.
But what about more complex shapes? E.g. a masked region along a coastline?

I thought this should be a common problem when applying a regionally confined forcing in a model. I would very much appreciate any hints.

Regards
Sebastian
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Received on Mon May 19 02:08:48 2014